// Copyright 2014 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_BASE_FLAGS_H_
#define V8_BASE_FLAGS_H_

#include <cstddef>

#include "src/base/compiler-specific.h"

namespace v8 {
namespace base {

    // The Flags class provides a type-safe way of storing OR-combinations of enum
    // values. The Flags<T, S> class is a template class, where T is an enum type,
    // and S is the underlying storage type (usually int).
    //
    // The traditional C++ approach for storing OR-combinations of enum values is to
    // use an int or unsigned int variable. The inconvenience with this approach is
    // that there's no type checking at all; any enum value can be OR'd with any
    // other enum value and passed on to a function that takes an int or unsigned
    // int.
    template <typename T, typename S = int>
    class Flags final {
    public:
        using flag_type = T;
        using mask_type = S;

        constexpr Flags()
            : mask_(0)
        {
        }
        constexpr Flags(flag_type flag) // NOLINT(runtime/explicit)
            : mask_(static_cast<S>(flag))
        {
        }
        constexpr explicit Flags(mask_type mask)
            : mask_(static_cast<S>(mask))
        {
        }

        constexpr bool operator==(flag_type flag) const
        {
            return mask_ == static_cast<S>(flag);
        }
        constexpr bool operator!=(flag_type flag) const
        {
            return mask_ != static_cast<S>(flag);
        }

        Flags& operator&=(const Flags& flags)
        {
            mask_ &= flags.mask_;
            return *this;
        }
        Flags& operator|=(const Flags& flags)
        {
            mask_ |= flags.mask_;
            return *this;
        }
        Flags& operator^=(const Flags& flags)
        {
            mask_ ^= flags.mask_;
            return *this;
        }

        constexpr Flags operator&(const Flags& flags) const
        {
            return Flags(*this) &= flags;
        }
        constexpr Flags operator|(const Flags& flags) const
        {
            return Flags(*this) |= flags;
        }
        constexpr Flags operator^(const Flags& flags) const
        {
            return Flags(*this) ^= flags;
        }

        Flags& operator&=(flag_type flag) { return operator&=(Flags(flag)); }
        Flags& operator|=(flag_type flag) { return operator|=(Flags(flag)); }
        Flags& operator^=(flag_type flag) { return operator^=(Flags(flag)); }

        constexpr Flags operator&(flag_type flag) const
        {
            return operator&(Flags(flag));
        }
        constexpr Flags operator|(flag_type flag) const
        {
            return operator|(Flags(flag));
        }
        constexpr Flags operator^(flag_type flag) const
        {
            return operator^(Flags(flag));
        }

        constexpr Flags operator~() const { return Flags(~mask_); }

        constexpr operator mask_type() const { return mask_; }
        constexpr bool operator!() const { return !mask_; }

        friend size_t hash_value(const Flags& flags) { return flags.mask_; }

    private:
        mask_type mask_;
    };

#define DEFINE_OPERATORS_FOR_FLAGS(Type)                                \
    inline Type operator&(                                              \
        Type::flag_type lhs,                                            \
        Type::flag_type rhs) ALLOW_UNUSED_TYPE V8_WARN_UNUSED_RESULT;   \
    inline Type operator&(Type::flag_type lhs, Type::flag_type rhs)     \
    {                                                                   \
        return Type(lhs) & rhs;                                         \
    }                                                                   \
    inline Type operator&(                                              \
        Type::flag_type lhs,                                            \
        const Type& rhs) ALLOW_UNUSED_TYPE V8_WARN_UNUSED_RESULT;       \
    inline Type operator&(Type::flag_type lhs, const Type& rhs)         \
    {                                                                   \
        return rhs & lhs;                                               \
    }                                                                   \
    inline void operator&(Type::flag_type lhs,                          \
        Type::mask_type rhs) ALLOW_UNUSED_TYPE;                         \
    inline void operator&(Type::flag_type lhs, Type::mask_type rhs) { } \
    inline Type operator|(Type::flag_type lhs, Type::flag_type rhs)     \
        ALLOW_UNUSED_TYPE V8_WARN_UNUSED_RESULT;                        \
    inline Type operator|(Type::flag_type lhs, Type::flag_type rhs)     \
    {                                                                   \
        return Type(lhs) | rhs;                                         \
    }                                                                   \
    inline Type operator|(Type::flag_type lhs, const Type& rhs)         \
        ALLOW_UNUSED_TYPE V8_WARN_UNUSED_RESULT;                        \
    inline Type operator|(Type::flag_type lhs, const Type& rhs)         \
    {                                                                   \
        return rhs | lhs;                                               \
    }                                                                   \
    inline void operator|(Type::flag_type lhs, Type::mask_type rhs)     \
        ALLOW_UNUSED_TYPE;                                              \
    inline void operator|(Type::flag_type lhs, Type::mask_type rhs) { } \
    inline Type operator^(Type::flag_type lhs, Type::flag_type rhs)     \
        ALLOW_UNUSED_TYPE V8_WARN_UNUSED_RESULT;                        \
    inline Type operator^(Type::flag_type lhs, Type::flag_type rhs)     \
    {                                                                   \
        return Type(lhs) ^ rhs;                                         \
    }                                                                   \
    inline Type operator^(Type::flag_type lhs, const Type& rhs)         \
        ALLOW_UNUSED_TYPE V8_WARN_UNUSED_RESULT;                        \
    inline Type operator^(Type::flag_type lhs, const Type& rhs)         \
    {                                                                   \
        return rhs ^ lhs;                                               \
    }                                                                   \
    inline void operator^(Type::flag_type lhs, Type::mask_type rhs)     \
        ALLOW_UNUSED_TYPE;                                              \
    inline void operator^(Type::flag_type lhs, Type::mask_type rhs) { } \
    inline Type operator~(Type::flag_type val) ALLOW_UNUSED_TYPE;       \
    inline Type operator~(Type::flag_type val) { return ~Type(val); }

} // namespace base
} // namespace v8

#endif // V8_BASE_FLAGS_H_
